The present invention generally relates to optical disk units (hereinafter referred to as recordable optical disk units) for driving recordable optical disks and rotating motor control apparatuses, and more particularly to a recordable optical disk unit and a control circuit and a LSI for a rotating motor control apparatus in the recordable optical disk unit.
Optical disks are used as devices for recording a large amount of information.
A general description will be given of the optical disk and a drive structure.
General CD-R and CD-E are writable (recordable) CDs (compact disks). The CD-R (CD-Recordable) is a once-writable CD (also referred to as CD-Write Once). On the other hand, the CD-E (CD-Erasable) is a multiple-times-writable CD (also referred to as CD-RW or CD-Rewritable).
These optical disks such as the CD-R and the CD-E are used with a drive shown in FIG. 1 when recording and reproducing information.
FIG. 1 is a functional block diagram showing an example of an important structure of an optical disk drive. FIG. 1 shows an optical disk 1, a spindle motor 2, an optical pickup 3, a motor driver 4, a read amplifier 5, a servo means 6, a CD decoder 7, an ATIP decoder 8, a laser controller 9, a CD encoder 10, a CD-ROM encoder 11, a buffer RAM 12, a buffer manager 13, a CD-ROM decoder 14, an ATAPI/SCSI interface 15, a digital-to-analog (D/A) converter 16, a ROM 17, a central processing unit (CPU) 18, a RAM 19, a laser beam LB, and an audio output signal Audio.
In FIG. 1, arrows indicate directions in which data mainly flow. Further, in order to simplify the drawing, only one representative signal line is indicated by a bold line and added to the CPU 18 which controls various parts in FIG. 1, and the illustration of the connections to the various parts is omitted.
The construction and operation of the optical disk drive are as follows.
The optical disk 1 is driven and rotated by the spindle motor 2. This spindle motor 2 is controlled by the motor driver 4 and the servo means 5 so that a linear velocity becomes constant. This linear velocity can be changed in steps.
The optical pickup 3 is built-in with a semiconductor laser, an optical system, a focus actuator, a track actuator, a light receiving element and a position sensor which are not shown, and irradiates the laser beam LB on the optical disk 1. This optical pickup 3 is movable in a sledge direction by a seek motor.
Based on signals obtained by the focus actuator, the track actuator, the seek motor, the light receiving element and the position sensor, the motor driver 4 and the servo means 5 carry out a control so that a spot of the laser beam LB is positioned at a target location on the optical disk 1.
In a read mode, a reproduced signal obtained from the optical pickup 3 is amplified by the read amplifier 5 and input to the CD decoder 7 after being binarized. The input binarized data is demodulated in the CD decoder 7 in accordance with an EFM (Eight to Fourteen Modulation).
Recorded data is modulated by the EFM in units of 8 bits, and according-to the EFM, 8 bits are converted into 14 bits and a total of 17 bits are obtained by adding 3 coupling bits. In this case, the coupling bits are added so that the number of "1"s and the number of "0"s become the same on an average. This is called "D.C. component suppression", and a slice level deviation of the reproduced signal is suppressed by cutting the D.C. component of the reproduced signal.
The demodulated data is subjected to a deinterleaving process and an error correction process. Thereafter, the data is input to the CD-ROM decoder 14 so as to improve the data reliability, and an error correction process is then carried out.
The data subjected to the two error correction processes is temporarily stored in the buffer RAM 12 by the buffer manager 13. The stored data when completed as sector data, is transferred in one operation to a host computer which is not shown, via the ATAPI/SCSI interface 15. In the case of musical data, the data output from the CD decoder 7 is input to the D/A converter 16 and obtained as an analog audio output signal Audio.
In a write mode, the data obtained from the host computer via the ATAPI/SCSI interface 15 is temporarily stored in the buffer RAM 12 by the buffer manager 13. The write operation is started in a state where a certain amount of data is stored in the buffer RAM 12, and in this case, it is necessary to first position the laser beam spot to a write starting point. This write starting point is obtained by a wobble signal which is prerecorded on the optical disk 1 by the zigzag of the track.
Absolute time information called ATIP is included in the wobble signal, and this absolute time information is obtained by the ATIP decoder 8. In addition, a synchronizing signal generated by the ATIP decoder 8 is input to the CD encoder 10, thereby making it possible to write the data at an accurate position on the optical disk 1.
The data stored in the buffer RAM 12 is subjected to a process of adding an error correction code and an interleaving process in the CD-ROM encoder 11 and the CD encoder 10, and is recorded on the optical disk 1 via the laser controller 9 and the optical pickup 3.
The EFM data drives the laser as a bit stream at a channel bit rate of 4.3218 Mbps (standard rate). The recording data in this case forms an EFM frame in units of 588 channel bits. A channel clock refers to a clock having a frequency of the channel bits.
The general construction and operation of the optical disk drive shown in FIG. 1 are as described heretofore.
A spiral guide groove is formed in the MD (mini disk), the CD-R (CD recordable: compact disk that can be written once), and the CD-E (CD erasable: compact disk that is erasable and writable a plurality of times). This guide groove makes a zigzag in a radial direction of the disk by an extremely small amount (for example, on the order of 0.03 .mu.m) at a constant spatial frequency (for example, 17,00 cycles/m: 1 period per 59 .mu.m) so that the rotation can be controlled to a CLV (Constant Linear Velocity).
When the drive drives the rotating motor so that this zigzag signal frequency becomes constant (for example, 22.05 kHz), it is possible to rotate the disk at a constant linear velocity (for example, 1.3 m/s).
Therefore, the guide grooves makes a zigzag, and a disk unit which controls the rotation of the disk by detecting the zigzag signal frequency is known (for example, Japanese Laid-Open Patent Application No.6-338066).
In addition, address information is frequency modulated (FM) and multiplexed to the zigzag signal frequency.
For example, the information "1" is modulated to 23.05 kHz, and the information "0" is modulated to 20.05 kHz.
Since the number of the information "1" and the number of the information "0" are made the same on the average, the CLV control is actually set so that an average frequency of the zigzag signal becomes 22.05 kHz.
The address information is called ATIP (Absolute Time In Pre-groove). Moreover, the zigzag signal is called wobble signal. This wobble signal is a carrier signal of the ATIP.
An apparatus which obtains an address signal from a carrier wave modulation component by carrying out a CLV control by controlling the rotation so that the carrier wave of the zigzag groove becomes constant, is also known (for example, Japanese Laid-Open Patent Application No.5-225580).
A 1-chip LSI which is used in the optical disk drive such as the CD-R drive, for example, is already on the market (for example, LC89590 manufactured by Sanyo Electric Company Limited of Japan and materials related to the explanation and application thereof).
Therefore, a circuit which carries out the CLV control in synchronism with the wobble signal, and a circuit which carries out the CLV control in synchronism with the address synchronizing signal (ATIPSYNC) of the ATIP, are both known as conventional techniques.
However, according to these conventional techniques, there is no disclosure as to the relationship of a rotation control circuit which is used when reproducing signals from a reproducing disk and a rotation control circuit which is used when rotating a recording disk.
Furthermore, the conventional techniques do not teach a rotation control in a data region which is partially recorded on the recording disk.
As described above under prior art, a circuit which carries out the CLV control in synchronism with the wobble signal, and a circuit which carries out the CLV control in synchronism with the address synchronizing signal (ATIPSYNC) of the ATIP, are both known as conventional techniques.
However, in the region of the recording disk recorded with the data, the wobble signal cannot be detected accurately in some cases because the wobble signal is distorted by the recorded data. For this reason, there is a problem in that the rotation control easily becomes unstable when the rotation control is continuously carried out using the wobble signal.
In order to improve a signal-to-noise (S/N) ratio of the wobble signal, the wobble signal must in general be detected via a narrow band bandpass filter (BPF). But when the target linear velocity is not yet reached, such as when making an access and starting the rotation, the wobble signal is in a state shifted from the passband of the bandpass filter and the wobble signal cannot be detected accurately.
Accordingly, there is a problem in that the rotation control easily becomes unstable in such cases.
Furthermore, it is also known to set a mode for controlling the rotation in synchronism wit the address synchronizing signal (ATIPSYNC) (above described LC89590 manufactured by Sanyo Electric Company Limited of Japan and materials related to the explanation and application thereof).
This mode is added because the wobble signal cannot be completely synchronized to the address information due to a bit slip or the like according to the rotation control using the wobble signal.
But since the address synchronizing signal (ATIPSYNC) has a low frequency of 75 Hz, the rotation control cannot be made in the high band, and there is an inconvenience in that a fine control is difficult to achieve.
In addition, according to the rotation control described above, an instruction from a CPU (microcomputer) or an external circuit must be used in general to switch the mode among a control mode of the reproducing disk, a control mode of a wobble signal, a control mode of an address synchronizing signal (ATIPSYNC), and the like. As a result, there are various problems in that the programming is difficult to perform, and the cost of the system increases due to the need for the external circuit.